The unannounced building work that has extensively damaged the rare Chinese-style King Yin Lei mansion displays a flagrant disregard for Hong Kong's physical heritage. It is a stark reminder of the urgent need for the government to develop a coherent and comprehensive policy to protect such treasures.

Tiles have been removed from the roof of the 71-year-old mansion, dents have been inflicted on its distinctive red bricks and other key features have been removed or destroyed. It is now a pitiful sight. It is almost as if the new owner wanted to chip away at the features that give the mansion its heritage value, leaving no reason to preserve it. Sadly, under the law, the owner has done nothing wrong. Such work is allowed as long as there is no structural damage to the building. The mansion, after all, was not even graded for its heritage significance. Had it not been for the vigilance of activists and neighbours, the work may have been completed before it even attracted public attention.

The government, in this instance, has acted speedily by declaring it a proposed monument. As a result, the destruction will have to stop immediately the building's new status is gazetted today. The freeze will buy some time - 12 months to be exact - during which antiquity officials will decide whether the mansion deserves permanent protection under the law. But the government's intervention, while welcome, has come too late. Extensive damage has already been done.

King Yin Lei is popular with tourists and locals alike because of its unique oriental design and craftsmanship. Yet, despite intense public scrutiny leading up to its sale in July for HK$430 million, the mansion was essentially no different from any other old building liable to be redeveloped. Even if it had been graded, it would not have provided much protection. There are 496 graded heritage buildings listed under a conservation policy consultation exercise put out by the government in January. But what protects them is public pressure, not the law. Only 83 structures have been declared monuments and given proper protection. Many of these buildings are public, or the owners are open to preservation proposals.

Critics, with some justification, have charged that the government is reluctant to take a more proactive role that may mean confronting owners bent on selling or redeveloping their prized properties. In any case, the Antiquities and Monuments Office does not have the resources and manpower to take on a more active role.

But the absence of a coherent and effective policy works against site owners as well. Owners will be confused about what they can do with their buildings once they are graded. There is no policy of compensating those who own graded properties that have not been declared monuments. Some owners will come under public pressure not to redevelop the sites, and be inclined to neglect them.

This is why there is an urgent need for the government to develop a coherent strategy. It may consider establishing a trust fund for this purpose. Adequate compensation, tax breaks and other financial incentives may be offered, so owners can maintain and upgrade their buildings and revamp them for more creative uses such as opening them to the public.

As Queen's Pier and now King Yin Lei have shown, Hong Kong people will not stand by and watch their heritage being destroyed. The government must be ready to put an effective policy in place now, to prevent further abuses.